Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. The present disclosure relates generally to data storage devices, and to systems and methods for such devices. In various examples, data modulation techniques in data storage devices such as flash memory devices are described.
Flash memories are one type of electronic non-volatile memories (NVMs), accounting for nearly 90% of the present NVM market. Today, billions of flash memories are used in mobile, embedded, and mass-storage systems, mainly because of their high performance and physical durability. Example applications of flash memories include cell phones, digital cameras, USB flash drives, computers, sensors, and many more. Flash memories are now sometimes used to replace magnetic disks as hard disks.
A flash memory device includes memory cells that are capable of storing a voltage charge, either a memory cell level of logic “1” or a memory cell level of logic “0”. That is, the cell voltage level corresponds to a logic level, or numeric representation of a binary digit. Changing the cell level (e.g., changing the cell voltage charge) changes the stored binary digit value. A limitation of conventional flash memories is the high cost of changing a cell voltage level from a first logic level to a second logic level, such as from logic “1” to logic “0”. To perform such a change, a “block erasure” operation is performed. Block erasures are typically performed when the data value in a cell or group of cells is changed to represent new values. The block erasure is relatively expensive in terms of resource utilization, such as time and electrical power to perform the block erasure. Operation of flash memory devices would be more efficient if such block erasure resource demands were reduced.